Search results for "SHELL"
showing 10 items of 748 documents
Shell proteome of rhynchonelliform brachiopods.
2015
7 pages; International audience; Brachiopods are a phylum of marine invertebrates that have an external bivalved shell to protect their living tissues. With few exceptions, this biomineralized structure is composed of calcite, mixed together with a minor organic fraction, comprising secreted proteins that become occluded in the shell structure, once formed. This organic matrix is thought to display several functions, in particular, to control mineral deposition and to regulate crystallite shapes. Thus, identifying the primary structure of matrix proteins is a prerequisite for generating bioinspired materials with tailored properties. In this study, we employed a proteomic approach to identi…
Multi-isotopic and trace element evidence against different formation pathways for oyster microstructures
2021
Geochimica et cosmochimica acta 308, 326-352 (2021). doi:10.1016/j.gca.2021.06.012
New isomers in the full seniority scheme of neutron-rich lead isotopes: The role of effective three-body forces
2012
The neutron-rich lead isotopes, up to Pb216, have been studied for the first time, exploiting the fragmentation of a primary uranium beam at the FRS-RISING setup at GSI. The observed isomeric states exhibit electromagnetic transition strengths which deviate from state-of-the-art shell-model calculations. It is shown that their complete description demands the introduction of effective three-body interactions and two-body transition operators in the conventional neutron valence space beyond Pb208. © 2012 American Physical Society.
Almond shell reuse: a viable non-conventional aggregate for sustainable building materials
2022
Bio-based or green architecture is a new way of designing and building in line with the European Green Deal and in light of the Circular Economy principles. The main green approach directs the whole construction life cycle to be eco-sustainable and environmentally friendly from the beginning to the end of the building process. Beyond the use of eco sustainable and highly performing structural materials, new technologies able of reduce the environmental impact of buildings must be used. This paper is aimed at reviewing the possible reuse of bio- wastes of agricultural origin whose massive production generates a number of issues for their treatment and disposal. In particular, this study will…
Proton-neutron pairing correlations in the self-conjugate nucleus 42Sc
2021
Collinear laser spectroscopy of the N=Z=21 self-conjugate nucleus 42Sc has been performed at the JYFL IGISOL IV facility in order to determine the change in nuclear mean-square charge radius between the Iπ=0+ ground state and the Iπ=7+ isomer via the measurement of the 42g,42mSc isomer shift. New multi-configurational Dirac-Fock calculations for the atomic mass shift and field shift factors have enabled a recalibration of the charge radii of the 42−46Sc isotopes which were measured previously. While consistent with the treatment of proton-neutron, proton-proton and neutron-neutron pairing on an equal footing, the reduction in size for the isomer is observed to be of a significantly larger m…
Effects of sample pretreatment and external contamination on bivalve shell and Carrara marble δ18O and δ13C signatures
2017
Abstract Stable isotope signatures of bivalve shells serve as important paleoclimate proxies. However, such data can be biased as a consequence of physical and chemical sample pretreatment and contamination during sampling. As yet, the potential isotope error induced by paleontological preservation techniques and specific methods used in bivalve sclerochronology have not been systematically assessed. To address these issues, homogenized powder of a well-preserved, aragonitic fossil shell, Glycymeris obovata (ca. 30 Ma old) as well as Carrara marble powder (calcite) were exposed to ultrasound, a set of different staining solutions and cleaning agents. In addition, these reference materials w…
Molluscan Shell Proteins: Primary Structure, Origin, and Evolution
2007
In the last few years, the field of molluscan biomineralization has known a tremendous mutation, regarding fundamental concepts on biomineralization regulation as well as regarding the methods of investigation. The most recent advances deal more particularly with the structure of shell biominerals at nanoscale and the identification of an increasing number of shell matrix protein components. Although the matrix is quantitatively a minor constituent in the shell of mollusks (less than 5% w/w), it is, however, the major component that controls different aspects of the shell formation processes: synthesis of transient amorphous minerals and evolution to crystalline phases, choice of the calciu…
Molluscan shell proteins
2004
Abstract The shell secreted by molluscs is one of the most remarkable examples of a matrix-mediated mineralisation performed outside living tissues. The calcifying matrix is a mixture of proteins, glycoproteins, and polysaccharides that precisely self-assemble and control the CaCO 3 polymorph (calcite, aragonite), the size, the shapes of the crystallites, and finally, the texture of the shell. In spite of several biochemical studies, the molecular aspects of the shell building are far from being understood. The present article makes an overview of the most recent molecular data on the proteinaceous components of the shell matrix. These data put into question the classical models of mollusca…
Modeling red coral (Corallium rubrum) and African snail (Helixia aspersa) shell pigments: Raman spectroscopyversusDFT studies
2016
Pigments from red coral (Corallium rubrum) and African snail (Helixia aspersa) shell were studied non-invasively using Raman spectroscopy with 1064-nm laser beam. The two observed bands because of organic pigments confined in biomineralized CaCO3 matrix at about 1500 and 1100 cm−1 were assigned to ν(CC) and ν(C―C), respectively. Both signals originate from polyene(s) of largely unknown structure, containing several conjugated CC bonds. The small peak at 1016 cm−1 in the Raman spectrum of coral pigment was assigned to in-plane ―CH3 rocking or structural deformation of polyene chain because of spatial confinement in the mineral matrix. The organic pigments in red coral and snail shell were pr…
Assessment for the mean value total dressing method: Comparison with coupled cluster including triples methods for BF, NO+, CN+, C2, BeO, NH3, CH2, H…
1997
Limited previous experience with the mean value total dressing (MVTD) method had shown that MVTD energies for closed shell systems are generally better than CCSD(T) ones compared to FCI. The method, previously published as total dressing 2′(td-2′), is based on the single reference intermediate Hamiltonian theory. It is not a CC method but deals in a great part with the same physical effects that CC methods that incorporate amplitudes of triples such as CCSDT or its CCSDT-1n approaches. A number of test calculations comparing to diverse CC methods, as well as FCI and experiment when available, have been performed. The tests concern equilibrium energies in NH3 and CH2, equilibrium energies an…